1. Field of the Invention
This invention relates to aqueous carbonaceous slurries and more particularly to aqueous coal slurries stabilized with water soluble polymers.
2. Description of the Prior Art
Transport is one of the major problems involved in use of particulate carbonaceous materials such as coal. One method of transport involves aqueous slurries. However, aqueous slurries of finely ground coal containing over 55 weight percent solids are difficult to pump with slurry pumps. This is because as the solids level is increased above 50 weight percent, water and solids tend to separate causing coal particles to build up in various areas in the pumping system. This dewatering of the slurry causes blockage and jamming in the pumping system.
On the other hand, decreasing the weight percent of water in aqueous coal slurries is desirable because water is a major contributor to the cost of transport and processing operations. The less water transported the greater the volume of coal that can be moved, resulting in transport efficiencies. Further, water resources are limited. Also, during burning of coal, a significant amount of heat is required to vaporize the water. As the weight percent of water decreases, the efficiency of the coal burning process increases. Hence, use of higher weight percent solids aqueous carbonaceous slurries than were heretofore feasible would be of great importance.
U.S. Pat. No. 4,242,098--Braun et al.--Dec. 30, 1980, describes addition of particular water soluble polymers, viz., poly (ethylene oxide, partially hydrolyzed poly (acrylamide), hydroxyethyl cellulose, the quaternary nitrogen-substituted cellulose ethers, xanthan gum, hydroxypropyl guar gum and carboxymethyl hydroxypropyl guar gum, to aqueous coal slurries to permit the extrusion, pumping and transport of aqueous coal slurries having higher solids content.
U.S. Pat. No. 4,282,006--Funk, Aug. 4, 1981, describes a pipeline pumpable coal water slurry having a high content of coal particles with a minimum of void spaces and a maximum of particles surface area to enhance dispersing effects generated by electrolytes and/or dispersing agents added to the slurry. For dispersing agents, see Column 29, line 53 to Column 31, line 9, including condensed mononaphthalene sulfonic acid and its sodium and ammonium salts (Column 30, lines 19 and 20).
U.S. Pat. No. 4,330,301--Yamamura et al., May 18, 1982, describes dispersants for aqueous coal slurries including naphthalene sulfonic acid formaldehyde condensates and their sodium and ammonium salts. See Column 2, lines 41 to 43 and Columns 5 and 6.